The invention relates to fixed ratio traction roller transmissions in which the contact forces applied to the traction surfaces of the transmission, which are in engagement with each other for the transmission of motion, are dependent on the torque transmitted through the transmission.
Traction roller transmissions in which large contact forces are applied to the rollers are described, for example, by Harold A. Rothbart in "Mechanical Design and Systems" Handbook, pages 14-8 and 14-9, McGraw-Hill, New York 1964. In the relatively simple arrangements of FIGS. 14.6 and 14.7 wherein the outer rings of planetary-type transmissions are slightly undersized to compress the roller arrangements therein, the surface pressure on the traction surfaces is always the same, that is, it is always high independently of the torque transmitted through the transmission.
In the arrangements shown on page 14-8 of said handbook, means are provided for engaging the traction surfaces with each other with forces which are dependent on the torque transmitted through the transmission.
In U.S. Pat. No. 771,541 a variable contact force is obtained by an outer ring structure which is compressed when a torque is transmitted. However, this arrangement requires sliding surfaces which have relatively high friction or a complicated lever arrangement which amplifies the reaction forces of the transmission to provide sufficient compression of the outer ring for its engagement with the traction rollers.